1. Field of the Invention
The present invention relates to the measurement of the distances covered and the speeds reached by walking and/or running people.
2. Description of the Related Art
As can be easily thought, to measure the distance covered by a person moving on foot is a much more complex operation than that for measuring the distance covered and the speed reached by vehicles moving on wheels.
Some electronic, commercially available devices for sportsmen are known which are able to count the steps and to calculate, with great approximation, the distance covered.
With regard to this, it should be appreciated there is no problem in counting the steps but it is very difficult to determine the distance and the speed at which the latter is covered. It is then evident that the length of the step, i.e. the distance between the two feet of the walker, should be measured every time.
Such operation may be carried out in one of the following ways:
A) Transmission and reception of an ultrasonic signal by suitable transducers measuring the time T taken by the signal and calculating the distance S, the speed of sound being known (S=V.times.T; V=speed of sound). PA1 B) Use of a radiofrequency system of very short range provided with a transmitter on one side and a receiver on the other side, both having a directional antenna. Thus a signal directly proportional to the distance is provided at the output of the receiver. PA1 C) Measurement of a magnetic flow and detection of the distance according to the amplitude (compass principle). PA1 D) Use of a modulated infrared transmitting-receiving system provided with an array of transmitting leds and receiving photodiodes so that the detection of the signal is made directional and then proportional to the distance.
In any case, whatever method is chosen, it is necessary to carry out some automatic compensations which are able to keep the signal constant as the outer varying conditions change. It should be noted that such changes can also be varied along the same path. In order to better explain such aspect, in case the radiofrequency system is used, it is sufficient to think to the difference between running on grass and running on reinforced concrete pavement. Actually, the reinforcement of the latter would cause an attenuation of the signal disturbing the operation of the system.
It should be noted that all of the necessary detection operations have to be synchronized with the positions of the feet (laid down or raised).
As far as the different methods mentioned above are concerned it should be noted that system A) based on the use of ultrasounds has to be discarded both because of the fragility of the transducers which cannot withstand the mechanical stress in such an application and the difficulty of protecting them from water splashes (rain, puddles, etc.).
System B) based on the use of radiofrequency signals has big application problems because it requires calibrations and is particularly sensitive to thermal variations. In order to overcome such problems it would be necessary to resort to a very expensive apparatus which would not be recommended for a commercial production.
The drawback of system C) using a magnetic flow consists in that it is strongly depending on the type of pavement on which the user runs or walks causing high variations of parameters and characteristics of the detection system.
To sum up, the method involving fewer problems of the measurement and display system is that of item D) above, i.e. that using an infrared transmitting/receiving system.